A Medium 10×10 Puzzle Solved with Shape Squeeze in 19 Steps

This 10×10 board rates as medium (difficulty score 825). Solving it from scratch takes 19 logical steps, using 7 techniques: Single cell, Row/column exclusion, Adjacency clear, Region confinement, Line confinement, Paired regions, Shape squeeze. Every step below is forced: nothing here is a guess.

1. First, every open cell left in this region sits in column A, so its marker has to land there; that clears every other open cell in the column.
2. Next, every open cell left in this region sits in column B, so its marker has to land there; that clears every other open cell in the column.
3. Then, every open cell left in this region sits in column C, so its marker has to land there; that clears every other open cell in the column.
4. After that, every open cell left in this region sits in column D, so its marker has to land there; that clears every other open cell in the column.
5. Now, place a marker at E9. Region has exactly one open cell left. Placing here clears the rest of row 9, column E, and its region. Placing here also clears its 2 touching neighbours.
6. From there, place a marker at A10. Region has exactly one open cell left. Placing here clears the rest of row 10, column A, and its region.
7. Following that, every open cell in row 5 belongs to the same region, so that region's marker has to be somewhere in this row; that clears every other open cell in the region.
8. First, together, two regions have open cells only in rows 7 and 8; with one marker each, those two markers have to fill exactly those two rows, so every other region's open cells there can be cleared.
9. Next, every open cell left in this region sits in column F, so its marker has to land there; that clears every other open cell in the column.
10. Then, every open cell left in this region sits in row 6, so its marker has to land there; that clears every other open cell in the row.
11. After that, place a marker at D3. Region has exactly one open cell left. Placing here clears the rest of row 3, column D, and its region. Placing here also clears its 1 touching neighbour.
12. Now, place a marker at C1. Region has exactly one open cell left. Placing here clears the rest of row 1, column C, and its region.
13. From there, place a marker at F4. Region has exactly one open cell left. Placing here clears the rest of row 4, column F, and its region. Placing here also clears its 1 touching neighbour.
14. Following that, place a marker at G2. Column 7 has exactly one open cell left. Placing here clears the rest of row 2, column G, and its region.
15. First, every remaining candidate in this region touches I6, so whichever candidate ends up marked will clear it, and it can be ruled out now regardless of which one wins.
16. Next, place a marker at J6. Region has exactly one open cell left. Placing here clears the rest of row 6, column J, and its region. Placing here also clears its 2 touching neighbours.
17. Then, place a marker at H5. Region has exactly one open cell left. Placing here clears the rest of row 5, column H, and its region.
18. After that, place a marker at I8. Region has exactly one open cell left. Placing here clears the rest of row 8, column I, and its region.
19. Finally, place a marker at B7. Region has exactly one open cell left.

The key move here was Shape squeeze. Once you can spot that, this board falls quickly. ∎